What are these grommet-y things holding together the motor housing for my security shutter, can I replace them, and with which tools?

January 7, 2009 8:32 AM

What are these grommet-y things holding together the motor housing for my security door (aka security roller shutter), and can I replace them, and if so what tools would be necessary?

Hello,

My place of business has some security doors, which are the standard security roller shutters, an example of which can be seen here.

I have to do a small amount of maintenance on them, which requires removing the cover of the motor housing at the top of the shutter. When the cover is new, it is attached to the rest of the housing with metal grommets of the type seen here. Here is another clearer shot with less context.

But, the repairguy who worked on one of the other gates before me cut through those or forced them off, and replaced them with philips-head screws, which tends to defeat the purpose of the exercise, since anyone can easily remove them in a jiffy and get access to the motor.

I fixed the shutter with the screws a few days ago, and it occurred to me that it was time for me to replace them with something more impregnable and more similar to the original grommets, if not identical.

Question 1: what are those grommets called? Can I buy them, is there a tool for re-inserting them from one side, and is there a tool for cutting through them? I realize that if I can cut through them, anyone can, but if they are very tightly attached and it takes a specialized tool, I'll be miles ahead of the philips-head situation. Having to destroy them and later put in new ones to do work is fine; maintenance has been required on average about once every three years.

Question 2: if question 1 doesn't bear fruit, any other suggestions for methods of securely attaching one piece of thin metal to another one, which can be primarily accomplished from one side of the metal (the access to the inside of the motor housing is very very tight when the cover is on) and which will be hard for a random stranger to screw around with? Given that I'll have plenty of time and access to a complete set of tools when I need to get it off again.

No advice to call a repairman, please. Having spent more than the cost of a new shutter on the repairman who left the philips head screws, the whole "is your stuff worth less than the cost of a professional?" argument has lost its ability to compel.

Thank you very much!

posted by anonymous to home & garden (6 comments total)

They're called "rivets" and there are a variety of ways to install them. You can get a little hand-powered riveting tool for, I don't know, $20 or $30. I don't know if there's a special tool to take them out, I've drilled them out the few times that I needed to get them open. They're basically a tube with both ends scrunched up and flared so that it won't come out. So, drilling at a flared end with a bit of a larger diameter than the tube bore, once you drill through the flared part, the tube can just be pushed through.

Another option might be to use a screw type which is much less common, i.e. security through obscurity. This is what various electronics manufacturers do, use screws that most people won't have tools to take off. I guess that's as good of a solution as any.

Is getting access to the motor really a problem? The shutters don't lock in any other way? For that matter, how are the shutters attached to the building? Just asking...

Why is this anonymous?
posted by RustyBrooks at 8:45 AM on January 7

They are rivets. You can replace them with a rivet gun of varying types, but it may be impossible to fit the riveter into the space needed after the unit was assembled in the factory, hence the use of common screws or bolts.

One option is to pull the screws and replace them with an uncommon headed security screw or bolt.
posted by Science! at 8:48 AM on January 7

They look like "pop rivets" (aka "blind rivets") to me. They come in a ton of different kinds and need a pop rivet gun to put them in. I've never used them myself, but I believe this sounds like the sort of thing they would be used for (thinnish sheet metal where you only have access to one side).
posted by samj at 8:52 AM on January 7

They look like normal aluminium pop rivets to me. You will need a rivet gun and some new rivets, but they are simple to install - just push them through the hole and squeeze the gun until it stops, release and push the gun flush against the rivet and repeat until it pops (hence the name) and the tail snaps off. Fully open the gun to remove the rivet tail and repeat.

Rivets are available (and the guns) from any hardware store/Home depot etc and are sized with the diameter of the hole (most likely 1/8 or 5/32 in your example is my guess) and also for the 'grip length' (ie the thickness of the two materials it is meant to be clamping together). Do your best to measure this, but err on the longer side for the rivet, as it just means you need more squeezes to pop it if you are too long. Don't go crazy, though, as you need a little clearance behind the hole to allow the rivet to go into before it pops.

ie if you guess that you are clamping two 1/8" panels, then a grip length of 1/4" to 3/8" or so is fine. Don't get one for 1" or anything daft.

Rivets just need drilling out when you need to get in there. The repair man is just making his life easier next time.
posted by Brockles at 8:57 AM on January 7

but it may be impossible to fit the riveter into the space needed after the unit was assembled in the factory, hence the use of common screws or bolts.

This may be true in some cases, but I suggest laziness on the repairman's part is most likely. If you can take a picture of them like that, there is more than enough room to get a rivet gun in - they need less room than a screwdriver, that's for sure.
posted by Brockles at 8:58 AM on January 7

Why is this anonymous?

Maybe the OP doesn't want anyone to know who they are, thus being able to find their poorly defended shop and descend upon it in the middle of the night with larcenous thoughts and a Phillips screwdriver.

Or, they just don't have an account.
posted by hallowdmachine at 12:05 PM on January 7